This invention relates to cleaning of semiconductor wafers and, more particularly, to an apparatus and method for wafer edge cleaning using a polish pad material such as is used in a chemical-mechanical polishing apparatus.
Chemical-mechanical polishing (CMP) is performed in the processing of semiconductor wafers and/or chips on commercially available polishing apparatus. The standard CMP polishing apparatus has a circular polishing pad and a rotating carrier for holding the wafer. A slurry is used on the polishing pad.
The semiconductor wafer undergoes a cleaning process subsequent to the CMP process. The cleaning process is necessary to prevent redeposition of foreign matter on the wafer and subsequent process operations, which inflicts yield detractors and loss of chips per wafer.
One conventional cleaning process comprises a brush cleaner. The semiconductor wafer is rotated by drive wheels while two brushes, or sets of brushes, one on the top and one on the bottom, clean the top and bottom surfaces. Some processes use a cleaning additive. Nevertheless, with such cleaning processes the outside perimeter of the wafer can hold some of the slurry and other foreign matter. These contaminants can later harden and crumble back on to the wafer resulting in the contaminants being redeposited.
The present invention is directed to solving one or more of the problems discussed above, in a novel and simple manner.
In accordance with the invention there is provided a method and apparatus for cleaning the edge of a wafer implemented in a wafer cleaning apparatus for cleaning a major surface of the wafer.
Broadly, there is disclosed herein a method for cleaning an edge of a wafer, the method being performed after a process employing a slurry on the wafer. The method comprises the steps of transporting the wafer using wafer drive wheels for rotating the wafer. The edge of the wafer is contacted with a polish pad material. The polish pad material is a material used in chemical-mechanical polishing of the wafer. The transporting and the contacting are performed in a wafer cleaning apparatus for cleaning a major surface of the wafer.
It is a feature of the invention that the contacting step comprises contacting the edge of the wafer with a guide wheel having the polish pad material on a circumference thereof.
The guide wheel is contoured having a circumferential groove receiving the edge of the wafer.
In accordance with another aspect of the invention an inflatable air bladder is disposed inwardly of the polish pad material to contour the polish pad material to the edge of the wafer.
It is another feature of the invention that the guide wheel is rotated in a direction opposite rotation of the wafer.
In accordance with another aspect of the invention, a dilute hydrofluoric acid is applied to the edge of the wafer. The dilute hydrofluoric acid is applied with a roll applicator.
In accordance with yet another aspect of the invention the edge of the wafer is selectively contacted with a brush. The brush comprises a rotating cup brush.
There is disclosed in accordance with another aspect of the invention an improvement in a brush cleaning apparatus for cleaning a major surface of a wafer and including wafer guide wheels for transporting the wafer. The improvement includes a polish pad material disposed on a circumference of the guide wheels. The polish pad material is a material used in chemical-mechanical polishing of the wafer. The polish pad material contacts an edge portion of the wafer during cleaning thereof, thereby removing contaminants from the edge portion of the wafer, so that edge cleaning is performed in situ in addition to the brush cleaning of the major surface of the wafer.
Further features and advantages of the invention will be readily apparent from the specification and from the drawings.